AMHERST — As the question of whether to legalize marijuana in Massachusetts looms on the horizon, Colorado’s top marijuana official on Saturday added new data to the debate: Since the state legalized recreational use of the drug, use by adults has not increased.

That was just one of the insights from Colorado’s legalization experience shared by Andrew Freedman, that state’s director of marijuana coordination, during his remarks at a conference held at the University of Massachusetts Amherst.

Northwestern District Attorney David Sullivan, meanwhile, expressed concerns about legalizing the drug for recreational use in Massachusetts, citing potential health impacts on teenagers and young adults.

The forum, hosted by the university’s Department of Health Promotion & Policy, brought together public health and government officials to discuss how good policy can make the difference if Massachusetts moves toward legalizing recreational marijuana.

Massachusetts voters in 2016 are expected to consider legalizing the drug through...